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    SubjectRe: [PATCH] SLUB use cmpxchg_local
    * Christoph Lameter (clameter@sgi.com) wrote:
    > On Mon, 27 Aug 2007, Mathieu Desnoyers wrote:
    >
    > > > a clean solution source code wise. It also minimizes the interrupt holdoff
    > > > for the non-cmpxchg_local arches. However, it means that we will have to
    > > > disable interrupts twice for the slow path. If that is too expensive then
    > > > we need a different solution.
    > > >
    > >
    > > cmpxchg_local is not used on the slow path... ?
    >
    > Right.
    >
    > > Did you meant:
    > >
    > > it means that we will have to disable preemption _and_ interrupts on the
    > > fast path for non-cmpxchg_local arches ?
    >
    > We would have to disable preemption and interrupts once on the fast path.
    > The interrupt holdoff would just be a couple of instructions.
    >

    Right.

    > The slow path would require disable preemption and two interrupt disables.
    >

    If the slow path have to call new_slab, then yes. But it seems that not
    every slow path must call it, so for the other slow paths, only one
    interrupt disable would be required.

    > Question is if this makes sense performance wise. If not then we may have
    > to look at more complicated schemes.
    >

    Yep, such as the arch_have_cmpxchg() macro that I proposed, but it
    really hurts my eyes... :(

    Mathieu

    --
    Mathieu Desnoyers
    Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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